Spin Splitting in Bulk Wurtzite Materials and Their Quantum Wells

• Main Authors: Chieh-lung Wu, 吳傑龍
• Other Authors: Ikai Lo
• Format: Others
• Language: en_US
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/67657505655757164224

博士 === 國立中山大學 === 物理學系研究所 === 99 === The spin-splitting energies in strained bulk wurtzite aluminum nitride (AlN) are studied using the linear combination of atomic orbital method. It is found that strain and crystal field induce not only a linear-k (αwz ) but also two cubic-k terms (γ’and λ’ ) in the two-band k．p Hamiltonian Hso=(αwz-γ’k2//+λ’k2z)(σxky-σykx)+H0so, where H0so=(-γ0k2//+λ0k2z)(σxky-σykx) is for ideal wurtzite and generates a cone-shaped minimum-spin-splitting (MSS) surface. As biaxial strain increases, the shape of the MSS surface changes from a hexagonal hyperboloid of two sheets in unstrained AlN to a hexagonal cone, and eventually becomes a hyperboloid of one sheet. The spin-splitting energies of first conduction band for A-plane and M-plane wurtzite are calculated by the sp3 linear combination of atomic orbital (LCAO). The results show the spin-splitting energies are dominated by linear-k term but contribution of cubic-k terms can not be neglected for larger k//. The parameter of linear-k and cubic-k terms are evaluated from the LCAO calculated spin-splitting energies fitting to two band k‧p model as increasing well width. The coefficients of linear-k and cubic-k terms decrease.